Apparatus for continuously crystallizing solutions by evaporation or cooling



May 30, 1939.

' R. 'BONATH APPARATUS FOR CONTINUOUSLY CRYSTALLIZING SOLUTIONS BY EVAPORATION OR COOLING Filed Jan. 8, 1937 Patented May 30, 1939 :PATENT -OFFICE APPARATUS non con'rmnousm' oars- TALLIZING sow-nous BY EVAPORATION on oo'oLmG Richard Bonath, Bussum, Netherlands, assignor to Werkspoor N. V., Amsterdam, Netherlands Application January 8, 1937, Serial N6. 119,682

In the Netherlands January 11, 1936 'IClaims.

This invention relates to apparatus for continuously crystallizing supersaturated solutions' or solutions tending to become/supersaturated by. evaporating or cooling, and more especially for I 5 cooling massecuite and like crystallized masses and for concentrating sugar juices and syrups.

In order tocarry out said crystallisation continuously it has been proposed to use a receptacle or a series of receptacles connected one hehind the other comprising a rotaryshaft. having secured thereto hollow plates mounted at right angles to the axis of the shaft and forming the cooling or heating elements. The solution to be crystallized may then be continuously supplied 5 at one end of the apparatus and'after having passed along the cooling or heating elements continuously be discharged at the opposite end of the apparatus for iurther treatment. These known crystallizers have hitherto been so conjected to uniform heat treatment during its passage through the apparatus, so that when using heat exchanging elements disposed at right angles to the longitudinal axis of the receptacle said'elements are provided with an equal area and with equal mutual spacihgQwherebyeach of the elementswithdraws from or transmits to the mass under treatment a substantial equal amount of heat. This known arrangement of cooling elements, however, presents the disadvantage that the supersaturation of the motherliquor increases towards the discharge end of the apparatus which is due to the fact that in the latter stage of the apparatus in tion, so that there is danger of a formation of false grain and the mass becomes so viscous in 40 the neighbourhood of the cooling elements that the transfer of'heat to the cooling elements isv that here also the supersaturation increases and false grain is formed. I V

The present invention has for its object to avoid the above described drawback and to this 5 end the cooling or heating elements are so' arstructed that the mass to be treated is sub-' which the mass has already obtained a considranged that the cooling or heating surface per volume-unit or the crystallizer decreases towards the discharge end of the apparatus.

According to a preferred embodiment of *the crystallisation trough, the heat exchanging el- 5 'ments of which consist 42f hollow plates secured,

at right anglesto a. rotary-shaft, said plates are so arranged that theirrelative spacing increases towards the discharge end l of the trough and has therefore the smallest value at the, entry 10 of the trough. With such an arrangement a greater amount of heat is withdrawn-in .a cool- ;ing apparatusat the entryxwhere the solution to be crystallized is still warm and has a smaller viscosity and consequently a higher rate of 'crys- 15 tallisation than ,nearer to the discharge end and such an intensive cooling is allowablein view of the higher rate of crystallisation without dan:

gerof generating a'too high'degree of supersaturation. At the discharge end of the appago ratus on the contrary, where the mass is highly concentrated and the rate of crystallisation is low. a much smaller amount ofheat is withdrawn from the mass, so that an unallowable high degree of supersaturationof the mother 25 liqu r and the formation of false grain are prevented. It is even possible to obtain a decrease of the supersaturation towards the discharge end of the crystallizenso that the saccharose content of the mother liquor reaches a value correo sponding to that of a. completely exhausted molasses. g

In consequence of the more intensive heat exchange at the supply end of the apparatus, where the rate of crystallisation has its highest value the crystallisation will be finished as rapid as possible so that the mass can be passed along the cooling .or heating elements with a higher rate of flow than in the known crystallizers which results in an increase of the capacity.

The invention will now be described in detail with reference to the accom nying drawing in which Figs. 1 and 2 show a l gituulnal sectional elevation and a cross section alongthe line 11-11 in .Fig. 1 respectively of an apparatus adapted to be used as a cooling trough.

' through stuffing boxes 5, e and the left hand side journal carries a driving element riot shownon the drawing, such as a,wor mwheel or a pulley.

Secured to the shaft Z are-a seriesof hollow sector-shaped plates I alternately arranged in juxtaposition and mounted at right angles to ,the shaft. The plates I extend through an angular distance of substantially 200 as clearly illustrated in Fig; 2. A pipe 8 for supplying cooling water extends in the right hand side journail andisconnectedtotheflrstplate I. Th cooling water flows through the plates which to this end are connected t6 each other by means of pipes 9 located Within the hollow shaft. The cooling water leaves the left 'hand side plate I by'means of the pipe II. The

plates are bailles it which force the cooling water to follow a zigzag path in the plates.

The trough is further provided with a conveyingfscrew blade secured to the hollow shaft 2 by means of arms not shown on the drawing. Said screw blade furthers the travel of the mass through the receptacle but it will be understood that the mass can as well be caused to-flow under the influence of gravity only.

In order that the trough may be completely emptied a slide valve I8 is provided in the rearface of the trough and near the bottom thereof. By increasing the relative spacing of the cooling elements a smaller cooling surface at the discharge end of the trough results. This desired characteristic could also be obtained by decreasing the area of the plates which may then be arranged at the same spacing as at the entry of the trough. K

The described apparatus can also be used for boiling thick juice and syrups, for which purpose the trough should be provided with an air-tight cover and. be connected with means adapted to create a vacuum therein.

What I claim is:

1. Apparatus for continuously crystalllzing sotions by evaporation or cooling comprising a receptacle having a shaft revolubly mounted therein, and a series of hollowplates secured-at substantially right angles to said shaft and through which a temperature changing medium flows, said plates being so arranged relative'to one another that their mutual spacing increases towards the discharge and of the apparatus.

. 2; Apparatus for continuously crystallizing solutions by evaporation or cooling comprising a receptacle having a shaft revolubly mounted therein, and a series of hollow plates secured atsubstantiallyrightanglestosaidshaitand through which a temperature changing medium flows, said plates being in the form of circular disks adapted to partially fill the cross sectional area of the receptacle and so arranged relative to one another that. their mutual spacing inparatus.

creases towards-the discharge end of the an- 3; In an apparatus for continuously crystalliz- 3 -ing solutions by evaporation or cooling, a recepcreasing towards the discharge end of the receptacle.

4. lnqan apparatus for continuously crystallizing solutions by evaporation or cooling a series of receptacles connected one behind the other the first of which being adapted to receive a continuous supply of the solution so that thesolution moves through the receptacles in series and is discharged from the last receptacle, a plurality of hollow heat exchanging-elements mounted in the receptacles so as to engage the solution, the heat exchanging surface involved by said elements pervolume-unit of the mass under treatment decreasing towards the discharge end of the apparatus.

- 5. In apparatus for continuously crystallizing solutions by evaporation or cooling, a receptacle and a shaft rotatably mounted therein, a'series of heat exchange elements carried by said shaft surface area of heat exchange elements near the 7 end of the receptacle first receiving the solution being greater than the surface ajrea of the heat exchange elements at the discharge end.

I. In a evaporation or cooling, a receptacle adapted to the receptacle and is discharged at the opposite end, a shaft mounted for rotation in the recep-' tacle. a plurality of hollow heat exchange ele-,

ments secured to the shaft in a spaced -relation therealong with the mutual spacing thereof intowards the discharge end of the receptacle. w

BONATH.

tus for crystallizing solutions by receive a continuous supply of the solution at one end thereof so that the solution moves through 

